Means for reducing heat transfer along shafts



V. IVANOFF June 1 7, 1952 MEANS FOR REDUCING HEAT TRANSFER ALONG SHAFTS Filed Dec. 16, 1947 w w u A Patented June 17, 1952 MEANS F6 1? REDUCING HEAT TEANSFER ALONG SHAFTS Victor Ivanoff, Bedford, England, assignor to Hayward Tyier & Co. Limited, Lutcn, England,

a British company Application December 16, 1947, Serial No. 792,105 In Great Britain January 29, 1946 Section 1, Public Law 690, August, 8, 1945 Patent expires January 29, 1966 3 Claims. 1

This. invention relates to means for reducing heat transfer along shafts and relates particularly but not exclusively to the prevention of heat transfer along the shaft of centrifugal pumps which may have to operate at high or variable temperatures.

The invention'consists broadly in making said shaft hollow over at least a portion of its length.

In order that the invention may be the more clearly understood an example thereof as applied to a combined pump and motor assembly will now be described, reference being made to the accompanying drawings wherein:

Figure 1 is a sectional elevation of the pump end of said assembly.

Figure 2 is a fragmentary sectional elevation illustrating a modification.

Referring first to Figure l the assembly is in general as described in my co-pending application Serial No. 792,013, filed December 16, 1947, and now Patent 2,598,547, dated May 27, 1952, and is identical with that described in prior applications Serial No. 687,823, filed August 2, 1946 (now Patent No. 2,461,821) and Serial No. 687,824, also filed August 2, 1946 (now Patent No. 2,450,143). Thus the pump structure therein illustrated is associated in one assembly with a driving electric motor as in said prior specifications aforesaid. In the present drawing the Whole of the motor is omitted save for the near end of the motor casing which is designated by the reference I. The pump impeller is designated by the reference 2. As in said prior specification the motor casing l and the pump casing 3 are embodied in one common casing, which has a reduced neck 3 between said motorand pump casings, in which neck is located one of the journal bearings for a shaft 5 which is common to both pump and motor.

Also, as in. said prior applications, the fluid Within the common casing is cooled by circulating it, from the upper end of the motor casing (not shown), through a coil immersed in a cooling tank (not shown), and back to the common casing through a hole in the wall of the reduced neck 4 by way of a pipe 6.

The impeller 2 is mounted on the lower extremity of the shaft '5 and is adapted to draw the fluid in coaxially through an inlet port I at the lower end of the pump casing, and deliver it radially through an outlet port =3 in the plane of said impeller. Between said impeller and said outlet port 8 is provided a diffuser 9. This is the subject of the aforementioned Patent No. 2,450,143 and will not be further described herein.

Also a series of stationary baffles II in planes transverse to the axis of the shaft 5 are provided around said shaft in the back cavity of the pump casing for the purpose of creating a number of layers of relatively stagnant fluid and thereby reducing the rate of heat flow through said back cavity. This is primarily the subject of the aforementioned Patent No. 2,461,821 and will not be further described herein.

In the present arrangement the shaft 5, for some distance from its lower end, is made hollow as at 30 by boring, and a plug element 3| is welded in the open lower end of said shaft.

The impeller 2 is mounted On an extension of this plug element. As shown the hollow cavity St in said shaft extends from the plug element 3|, that is from the region of the pump casing into the region of the aforesaid reduced neck.

The hollow cavity 30 in said shaft is filled with the same liquid as that being pumped, said liquid having access to said cavity, from the pump casing 3, by way of a small breathing hole 32, which, as shown, is located within the upper end of the sleeve which carries the baffles II.

It is known that the rate of heat transfer through liquid is less than that through solid metal, and since the speed of rotation may be considered uniform the liquid in the cavity 30 will soon rotate at the velocity of the shaft without relative motion and only natural convection will exist to transfer heat through the cavity.

The circumferential Wall of the cavity 30 is made as thin as possible consistently with it being sufficiently strong to transmit the power from the motor to the pump, and to resist whirling and unbalanced hydraulic loads.

In some cases, particularly when the shaft is vertical and the hot conditions exist at the lower end as in Figure 1, a liquid baffle may be provided in the cavity 38 for the purpose of reducing heat transfer caused by thermal convection in the axial direction. A convenient form of such baffle is shown in Figure 2 and consists of a number of individual transverse disc-shaped baffle plates 33 threaded on to an axial stem 34 which is rigidly secured to the shaft, spacing sleeves 35 being provided on the stem for spacing said baffle plates at intervals longitudinally of the shaft. It will be seen that the circumferential edges of said baflle plates 33 are close to the inner periphery of the cavity as.

By this invention although the pump may have to be at a temperature of several hundred degrees it is relatively easy to maintain the motor at a suitable low temperature.

The invention may also usefully be employed in pumps dealing with high temperature liquids to reduce the rate of heat flow along a pump shaft into the stufling box and bearings.

I claim:

1. An apparatus comprising a shaft along which heat tends to be transferred, said shaft being hollow over at least a portion of its length, a body of liquid in the hollow interior of said shaft, and a plurality of individual transverse baflles spaced along said shaft in the hollow interior thereof with their circumferential edges close to the inner periphery of said shaft so as to reduce heat transfer by thermal convection longitudinally of said shaft.

2. A pump comprising a pump casing having a liquid inlet and an outlet communicating with the interior thereof, a rotary shaft extending into said pump casing, a, rotary impeller mounted on said shaft in said pump casing, said shaft being hollow over at least a portion of its length, and having a small hole extended through the wall, thereof for establishing communication between the hollow interior of said shaft and the inside of said casing, the hollow interior of said shaft being adapted to contain a body of the same liquid which is being pumped for impeding the transfer of heat from said impeller along said shaft, and said small hole constituting a breathing hole to enable the-liquid to pass between the inside of said casing and the hollow interior of said shaft.

3. An apparatus comprising a rotatable shaft along which heat tends to be transferred, said shaft having a coaxial cylindrical bore throughout at least a portion of its length, a body of liquid enclosed in said bore, an inner rod mounted coaxially within said bore, and a plurality of individual transverse circular baffles carried on said rod so as to reduce the flow of the liquid longitudinally of the shaft.

VICTOR IVANOFF.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 413,925 Blanchard Oct. 29, 1889 1,834,836 Goodwin Dec. 1, 1931 1,953,540 Ogden Apr. 3, 1934 2,239,228 Hankison Apr. 22, 1941 2,256,345 Mart Sept. 16, 1941 2,439,447 Buck et al. Apr. 13, 1948 2,450,143 Howard et a1 Sept. 28, 1948 2,461,821 Howard et al Feb. 15, 1949 

